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I started a code-intensive work in extjs/extjs6 : make the renderer
and elems in extjs6 inherit from those in extjs. this will enable us
to move lino.modlib.extjs.elems to lino.core.elems and to use those
layout elements as widgets in the forms ui. I am not yet 100% of my
coup, but if i am right, this should come before starting the new
lino.modlib.forms ui.